Here in UK people get called Jock, Paddy, Taff, Geordie, Scowser and, as far as I know, a few other things...are they offended? Not that I know of, and I live here.
Americans often call British people Limeys. British people often call North American people Yanks, or even Canucks - are THEY offended?
Well, not unless the American being addressed came from any of the the former Confederate states, or Texas.
Sunbeam, you should hear what the Americans call each OTHER, let alone us furriners.
'Racist'? Gimme a break.